1. Technical Field
The present invention concerns a tape cartridge in which a flexible, elastic drive belt contacts the tape which is wound on tape spools and whereby movement of the belt causes movement of the tape between the spools.
2. Background Information
Belt driven tape cartridges are frequently used to interface with computers where rapid acceleration and deceleration of the tape are required. U.S. Pat. No. 3,692,255 disclosed such a patent in which the magnetic recording tape is convolutely wound on two tape spools by an endless flexible belt in frictional contact with the tape on both spools. The endless flexible belt is wrapped around and driven by a capstan within the cartridge. The capstan itself is driven by a motor drive roller or drive puck which is external to the cartridge and is a portion of a recording/playback tape recorder mechanism into which the cartridge is inserted. The motor drive roller engages the capstan by means of an access opening provided in a wall of the cartridge.
Unfortunately, during operation of the cartridge, a static electric charge builds up on the capstan from the frictional contact between the motor drive roller and the capstan. If this static electric charge is not dissipated, a sudden discharge may result which may cause erroneous signals in the electronics of the tape recorder mechanism. In addition, it is important to produce the capstan of materials that can withstand the friction caused between the capstan and its mounting pin, the capstan and the cartridge surfaces, the capstan and the drive puck, and the capstan and the drive belt during operation.
Metal capstans, which would generally satisfy both the charge dissipation and wear resistance requirements of the capstan, are generally considered too expensive and may contribute to charge build-up on other tape cartridge components. Attempts have been made in the past to use polymers which had been made conductive by the addition of relatively large amounts of carbon. These capstans frequently did not display adequate wear resistance.
U.S. Pat. No. 4,607,808 attempted to solve the problem by using a two piece capstan design. The inner sleeve which surrounds the mounting pin included a polytetrafluoroethylene-filled acetal resin, while the remainder of the capstan comprised a carbon-filled acetal resin. Such a two piece design presents more difficulties in manufacture than a one piece design, thus an inexpensive, wear resistant, and charge dissipating one piece capstan design was desirable. International Patent Publication WO 91/13017 purports to have achieved a one piece, wear resistant, charge dispersing tape cartridge capstan comprising a resin matrix having a carbon fiber component and a fluorocarbon component therein.
Throughout these various modifications the geometry or structure of capstans remained substantially the same.